They were a package deal to keep the networks (Fox, in this case) from paying twice - two conference deals - for the LA market. I detest Oregon, but they'd have been the second choice in a vacuum. Stanford and UW for different reasons would be next, UCLA, Utah and ASU nearby. Of the 10 public Pac-12 schools that must report, UW athletics has the highest income and budget, in an effective tie with UO.
UCLA obviously tips the needle in basketball, but if football is paying the way, they're not second choice in the conference. Eliminating the LA market for anyone else was the reason it went down like this. Otherwise why not grab Arizona too?
USC and Oregon recruit nationally. I doubt the Trojans lose much sleep over Duck recruiting. If they do, they're still a giant pussy that's going to get reamed in the B1G. May it ever be so.